This invention pertains to earth boring tools and more particularly to a fixed blade non-rotating stabilizer especially adapted for drilling large diameter blind holes, e.g., over 30 inches in diameter.
In big hole drilling the tubular drill stem usually is provided at its lower end with a stool to the bottom of which is bolted a drilling cutter assembly or drill bit. An assembly of tools such as stabilizers and weights are spindled on the drill stem, the lower end of the assembly being supported by the stool. Usually the tool assembly merely rests in frictional engagement with the stool although in some cases the stem has been provided with a clutch jaw fixed thereon and engageable with a clutch jaw in the stabilizer skirt to positively prevent relative rotation of the stabilizer sleeve on the drill stem. Sometimes the stabilizer has been formed integral with the stool itself. Sometimes the stem is omitted and the tools are provided with flanges which bolt together to form an assembly to transmit torque to the drill bit or cutter assembly.
Fixed blade non-rotating stabilizers are well known for use both in small diameter holes such as oil wells and blast holes and in big holes. Various forms of anti-friction bearings have been used, at least with smaller size stabilizers. See for example the copending United States patent applications of applicant's assignee, Ser. Nos. 720,695; 720,954; 721,089; 721,090 filed Sept. 7, 1976. In connection with big hole stabilizers, marine bearings for radial loads have been used. Also steel thrust plates with bronze thrust bodies held to one side thereof by cap screws have been employed, the thrust plates being fastened to the rotating part of the stabilizer.
Difficulty has been experienced with the thrust bearings for big hole stabilizers because of the heavy weight involved. For example the non-rotating body of the stabilizer may weigh over a ton.
Roller stabilizers for big hole drilling are disclosed in U.S. Pat. to applicant's assignee Nos. 3,302,983 and 3,413,045, which disclose the use of marine bearings and of roller thrust bearings for the stabilizer rollers. Also, the latter patent shows the use of pinned and apertured flanges for making flanged connections between a big hole stabilizer and a drill bit and drill collar. However these patents are not concerned with bearings for non-rotating stabilizers, nor the stacking of big hole tools about a drill stem, nor the provision of means to insure that relative rotation occurs at the bearings between the non-rotating stabilizer body and its journal or inner sleeve rather than between the sleeve and the drill stem.